pH-Sensitive Multiliposomal Containers for Encapsulation and Rapid Release of Bioactive Substances.

A new method of the design of stimuli-sensitive multiliposomal containers for encapsulation and controlled drug release is described. Despite quite a wide choice of pH-sensitive containers, there is still a considerable challenge to synthesize those that respond quickly to small variations in pH and release most of the encapsulated drug in a short time. The suggested AMS-containing multiliposomal complexes demonstrated an excellent rate of encapsulated substance release under altering the pH of the outer solution. To improve the efficiency of the delivery of bioactive compounds to target cells and to increase the therapeutic effect, pH-sensitive liposomes were concentrated on the surface of the carrier- PEG-coated cationic liposomes. A pH-sensitive ampholytic derivative of cholan-24-oic acid embedded into the membrane of anionic liposomes allowed the rapid release of the cargo in the areas of low pH, such as tumors, inflammation sites, etc. The diameter of the complexes was optimized for passive targeting and typically ranged from 250 to 400 nm. The biodegradability of liposomes ensured enzymatic destruction of the multiliposomal containers and their elimination from the body after performing their transport function. The multiliposomal complexes and products of their biodegradation demonstrated low cytotoxicity. The composition of multiliposomal complexes, in particular, the amount of PEGylated lipid in the bilayer, was estimated to provide a high speed of the cargo release upon changing the pH. The novel developed pH-sensitive containers show potential for biomedical applications.